Clarify emojis have to be set on the emoji status

What does this MR do and why?

The roulette does not detect emojis within the text input, only within the emoji selector.

I've seen multiple colleagues having this confusion, as it's not super clear in the docs. So the roulette emoji detection was failing for them.

Additionally, I'm removing :: from the emoji text recommendation. Since emojis cannot be found via the emoji selector with the colons.

References

Please include cross links to any resources that are relevant to this MR This will give reviewers and future readers helpful context to give an efficient review of the changes introduced.

Here's how the emoji is detected:

`https://gitlab.com/gitlab-org/gitlab-roulette/-/blob/309096401e88ec9a7fc8c22ee1a58af00a4f0f72/lib/team_member.rb#L131-132``

The gitlab_status object is read a URL json object for the contributor. Example for myself:

$ curl https://gitlab-org.gitlab.io/gitlab-roulette/roulette.json | jq '.[] | select(.username == "Alexand").gitlab_status'

{
  "emoji": "ant",
  "message": "Please ping me when you desire my attention. Maximum :two: reviews",
  "availability": "not_set",
  "message_html": "Please ping me when you desire my attention.",
  "clear_status_at": null
}

I.e., in the above example, 2️⃣ wouldn't be detected for myself. What would be detected is 🐜, which does nothing for the roulette.

MR acceptance checklist

Please evaluate this MR against the MR acceptance checklist. It helps you analyze changes to reduce risks in quality, performance, reliability, security, and maintainability.

Screenshots or screen recordings

Screenshots are required for UI changes, and strongly recommended for all other merge requests.

Before	After

How to set up and validate locally

Numbered steps to set up and validate the change are strongly suggested.